1. Field of the Invention
The present invention relates to an organic EL device including a plurality of organic EL elements and a method of manufacturing the same, and in particular to technology that suppresses time-dependent deterioration of the organic EL elements.
2. Description of the Related Art
In recent years, an organic EL device in which organic EL elements are disposed on a substrate has been studied and developed as a display device. The organic EL device has the following advantages, for example. Firstly, since the organic EL elements themselves emit light, the organic EL device having such organic EL elements has an excellent visibility. Secondly, since such organic EL elements are solid state components, the organic EL device has an excellent impact-resistance. With such advantages, the organic EL device has been widely used as a display of TV or a display of a compact electronic device such as a mobile telephone.
The organic EL element is a current-drive type light emitting element, and has a structure in which a light-emitting layer is provided between a pair of positive and cathodes. The light-emitting layer usually includes layers that are placed on top of each other. Examples of the layers are a hole-injection layer, a hole-transport layer, an electron-transport layer and an electron-injection layer as well as an organic light-emitting layer. Here, the organic light-emitting layer causes an electroluminescence phenomenon by a recombination of carriers.
When the organic EL device is in use, moisture and oxygen included in a surrounding environment of the device possibly enter the device. Unfortunately, each of layers that compose the light-emitting layer is often formed with use of a material that is weak in moisture and oxygen. These layers are possibly altered in reaction to the moisture and oxygen that have entered the device. This causes generation of a nonluminescent portion (dark spot) in a display area and a decrease in luminance, in some cases. In order to solve the problems, Patent Literatures 1 and 2, for example, disclose technology of protecting the light-emitting layer from moisture and oxygen that exist in the surrounding environment of the device.
FIG. 8 shows a sectional view of a main part of an organic EL device pertaining to the Patent Literature 2. A display unit 31 is provided on a supporting substrate 32. On the display unit 31, a plurality of organic EL elements are arranged in a matrix (hereinafter, the display unit 31 and the supporting substrate 32 are collectively referred to as an array substrate 33). A sealing substrate 34 is disposed opposite the array substrate 33. A sealing member 35 is formed to extend to seal a gap between the array substrate 33 and the sealing substrate 34 so that the display part 31 is protected from the surrounding environment of the device. Even if the sealing member 35 is formed to extend to seal a gap between the array substrate 33 and the sealing substrate 34, a factor such as time-dependent deterioration of the sealing member 35 causes moisture and oxygen to enter the device from the surrounding environment of the device in some cases. This possibly causes a deterioration of the light-emitting layer. Thus, a further countermeasure is taken of disposing a desiccant 36 in a recess 37 formed on an inner surface of the sealing substrate 34. Here, the desiccant 36 absorbs moisture and oxygen that have entered from the surrounding environment of the device.
3. Patent Literatures
[Patent Literature 1] Japanese Patent Application Publication No. 2000-223264.
[Patent Literature 2] Japanese Patent Application Publication No. 2007-103317.